Goss Grains Research Articles

Texture and bendability evolution mechanism of 6063 aluminum alloy tube formed by free-bending technology employing cross-scale numerical modeling

With the improvement of application requirements, the combination of precise shape and high performance of tube components has become a burning issue. This work investigates the free-bending process of 6063 aluminum alloy tubes using cross-scale numerical modeling. The cross-scale framework integrates macroscopic finite element model (FEM) and crystal plasticity finite element model (CPFEM) through strain history. CPFEM exhibits excellent agreement with the macroscopic FEM and experimental results for both the Mises stress and texture evolution. Predictions indicate that as bending deformation increases, the volume fractions of the initial Cube texture decrease, while the Goss texture component increases. The overall texture strength continuously decreases. Meanwhile, slip mode plays a critical role in texture evolution, causing similar trends in the inner and outer bend regions. Additionally, the findings from the cross-scale simulation accurately predict the detailed texture evolution of the 6063 aluminum alloy tube under various feeding speeds. The development of Goss texture in various forming regions and the formation of substructures within Goss-oriented grains are primary factors contributing to reduced tube formability, which could illustrate the primary mechanisms for variation in tube bendability effectively. The proposed cross-scale method lays the foundation for research on complex spatial tube components as well. Moreover, cross-scale simulation facilitates the prediction of macroscopic deformation and microstructural evolution in critical regions of tube components, allowing for the optimization of bending processes based on cross-scale simulation results.

Influence of annealing treatment on grain growth, texture and magnetic properties of a selective laser melted Fe-6.5 wt% Si alloy

The high-density Fe-6.5 wt% Si soft magnetic alloy samples were prepared using selective laser melting (SLM) technology. Annealing treatments with different temperatures were employed to promote grain growth. The microstructure, texture and magnetic hysteresis loops were characterized, aiming to investigate the relationship between microstructure and magnetic properties. The as-printed Fe-6.5 wt% Si alloy had weak texture and low density of ordered phases, and was featured by coarse grains in the top-view section and columnar grains in the side-view section. After annealing at 800 °C–1000 °C, the textures were slightly weakened, while the grain growth was not significant. Increasing the annealing temperature to 1100 °C led to abnormal grain growth behaviors. The grains of the as-printed Fe-6.5 wt% Si alloy showed randomly abnormal growth behaviors rather than oriented growth, which may be related to the low stored energy and initial size advantage before annealing. After annealed at 1100 °C for 1 h, the abnormal grain growth and the formation of large Goss ({110}<001>) and Cube ({100}<001>) grains resulted in microstructure coarsening and texture optimization. Thus, the corresponding ring-shaped sample exhibited excellent magnetic performance. The magnetic induction B8 is 1.21 T, the maximum relative permeability is 14.71 × 103 and the core loss P10/50 is 11.69 W/kg.

Evolution and mechanism of recrystallization microstructure and texture in GH3536 superalloy foil and their influence on strength performance

To achieve isotropic strength in GH3536 foil, this study investigated the influence mechanism of initial recrystallization microstructure and texture characteristics of GH3536 superalloy foil with different cold-rolled reduction rates (referring to the reduction rate in thickness) on annealing recrystallization microstructure, including secondary recrystallization microstructure, and texture. This was studied by controlling the cold-rolled reduction rate and annealing temperature, in conjunction with microstructure and texture analysis. Meanwhile, this study clarified the dependency of strength performance on recrystallization microstructure and texture. The results of this study indicate that the Coincidence Site Lattice (CSL) grain boundaries and High Energy (HE) grain boundaries did not show significant superiorities, and were not the primary reasons for the formation of Brass ({011}<211>) and Goss ({011}<100>) textures, as well as secondary recrystallization. Instead, by controlling the cold-rolled reduction rate, the initial recrystallization stage formed a significant quantity and size superiority of α-fiber texture ({110}∥ND) in each grain size range. This led to preferential growth, and even abnormal growth of Brass and Goss grains in subsequent high-temperature annealing processes. The control of the α-deformation fiber texture was identified as the driving factor behind the formation of the initial recrystallization texture due to the cold rolling reduction rate. Cold-rolled processes with a deformation amount greater than 40 % yielded a quantity superiority of α-fiber texture shear bands and an appropriate stored energy advantage. This facilitated the nucleation and effective growth of more α grains, while suppressing the random growth of grains with γ-fiber texture ({111}∥ND). Ultimately, a quantity and size superiority was achieved in the initial recrystallization stage. The tensile strength of GH3536 foil was controlled by grain size and texture. By controlling the deformation amount to approximately 30 %, GH3536 foil was successfully produced with no pronounced orientation texture and isotropic strength.

Machine Learning-Aided Analysis of the Rolling and Recrystallization Textures of Pure Iron with Different Cold Reduction Ratios and Cold-Rolling Directions.

We performed a machine learning-aided analysis of the rolling and recrystallization textures in pure iron with different cold reduction ratios and cold-rolling directions. Five types of specimens with different cold reduction ratios and cold-rolling directions were prepared. The effect of two-way cold-rolling on the rolling texture was small at cold reduction ratios different from 60%. The cold reduction ratio in each stage hardly affected the texture evolution during cold-rolling and subsequent short-term annealing. In the case of long-term annealing, although abnormal grain growth occurred, the crystal orientation of the grains varied. Moreover, the direction of cold-rolling in each stage also hardly affected the texture evolution during cold-rolling and subsequent short-term annealing. During long-term annealing, sheets with the same cold-rolling direction in the as-received state and in the first stage showed the texture evolution of conventional one-way cold-rolled pure iron. Additionally, we conducted a machine learning-aided analysis of rolling and recrystallization textures. Using cold-rolling and annealing conditions as the input data and the degree of Goss orientation development as the output data, we constructed high-accuracy regression models using artificial neural networks and XGBoost. We also revealed that the annealing temperature is the dominant factor in the nucleation of Goss grains.

Numerical modeling of shear band effect on Goss grain recrystallization in electrical steels: Crystal plasticity finite element and phase field modeling

This study investigates the effect of shear band evolution on the nucleation of Goss {110}<001> texture during the primary recrystallization of 3.24 wt% Si grain-oriented electrical steel. Nucleation at the early stage of primary recrystallization of the steel is explored both experimentally and numerically. The experimental approach involves cold rolling the steel specimens to obtain a thickness reduction ratio of 76 % and then applying heat treatment to them at 600 °C for less than 1 min. The numerical simulation employes crystal plasticity (CP) finite element model (FEM) to simulate the plastic deformation induced by the dislocation slips on predefined slip systems and non-crystallographic shear bands during cold rolling. Based on the CPFEM results, the generalized strain energy release maximization (GSERM) model is used to predict the preferential orientation probability of recrystallized nuclei for the steel by considering shear band formation. Subsequently, the microstructure evolution during the early stage of primary recrystallization of the steel is simulated using the phase field model (PFM). The developed CP model successfully predicted shear band activation and evolution in the γ-fibers centered on the {111}<112> texture component. The model also demonstrated that shear bands would be the preferred nucleation sites at the early stage of primary recrystallization because of their high stored energy. Moreover, by coupling with the GSERM model, the PFM could reproduce the nucleation of Goss grains at the beginning of primary recrystallization in shear bands.

The origin of {113}&lt;361&gt; grains and their impact on secondary recrystallization in producing ultra-thin grain-oriented electrical steel

Abstract Ultra-thin grain-oriented electrical steel with a thickness of 80 µm is produced by one-step-rolling with industrial grain-oriented electrical steel. The research employs electron back-scattering texture analysis technique to investigate the evolution of deformation and recrystallization textures in this specific steel. Emphasis is placed on examining the origin of {113}&lt;361&gt; grains and their consequential impact on secondary recrystallization. It is revealed that primary, secondary, and tertiary recrystallization phases are integral during the annealing process. The origin of surface {113}&lt;361&gt; grains were result of initial deviated Goss grains with specific shear deformation behavior in cold rolled ultra-thin strips. Additionally, the influence of these grains on texture evolution is predominantly evident during secondary recrystallization. These grains potentially undergo abnormal growth in secondary recrystallization, exploiting high-energy grain boundaries among Goss grains. This phenomenon consequently leads to the diminution of the sharp Goss texture formed during primary recrystallization. Given the magnetic properties and predominant applications of ultra-thin grain-oriented electrical steel in medium-frequency fields, it is recommended to prepare ultra-thin grain-oriented steel during primary recrystallization phase.

Short-process preparation of grain-oriented electrical steel

The conventional production line of grain-oriented electrical steel (GOES) is long and the columnar grains in the cast slabs have adverse effects on GOES. In this paper, the short preparation process for GOES using top side-pouring twin-roll strip casting (TSTRC) was investigated. The results show that TSTRC can prepare cast strips with equiaxed grains. Conventional slab reheating, hot rolling, and normalization can be eliminated. The origin of Goss grains and the preparation of inhibitors were studied.

Effect of Gradient Heat Conduction on Secondary Recrystallization of Grain-Oriented Silicon Steel

The grain-oriented silicon steels were subjected to gradient heat conduction during high-temperature annealing by using thermal insulation cotton. The macrostructures of samples subjected to circumferential gradient heat conduction showed a “petal-like” morphology with peripheral columnar grains and central equiaxed grains, while samples subjected to transverse gradient heat conduction showed a morphology with approximately 50% columnar grains and 50% equiaxed grains. The grain orientations, magnetic domains as well as magnetic properties in different regions were detected. Results showed that the magnetic induction intensity of cylindrical grains was better than that of equiaxed grains while the iron loss was worse, which indicated that a fast heating rate during high-temperature annealing was conducive to the accuracy of Goss grains. The magnetic domains in columnar grains were wider than the equiaxed grains, which resulted in poorer iron loss. A theory of the competitive growth among secondary Goss grains was proposed. Under the condition of gradient heat conduction, once the Goss grains with the fastest heat conduction grew up abnormally, they would compete with other Goss grains which were supposed to survive in traditional processes and swallow up them until adjacent to the secondary equiaxed grains which were later developed.

The role of primary recrystallization microstructure in secondary recrystallization of Goss grain in industrial low-temperature grain-oriented silicon steel

Low-temperature grain-oriented silicon steel has very excellent magnetic properties along the rolling direction. During industrial mass production, slight process fluctuations can directly lead to variations in the primary recrystallization microstructure, which in turn can have a dramatic effect on the magnetic properties of the final product. However, it is unclear how different primary recrystallization microstructures influence the magnetic properties of the industrial final products, making it difficult to further optimize the production process of industrial low-temperature grain-oriented silicon steel. Therefore, it is very important to clarify the transformation behavior of different primary recrystallization microstructures and their influences on the transformation behavior of inhibitors during the high-temperature annealing process. Here, we analyzed the differences between two primary recrystallization microstructures in terms of microstructure homogeneity, Goss grain characteristics and texture characteristics and investigated the secondary recrystallization behavior of Goss grains and the dissolution behavior of inhibitors in these two primary recrystallization microstructures during high-temperature annealing. Based on the results of this work, it was found that a finer primary recrystallization microstructure could be more favorable to the formation of a sharp Goss texture, which in turn could significantly improve the magnetic properties, and in addition, new insights into the transformation behavior and the grain boundary pinning behavior of inhibitors during high-temperature annealing process were established. The results of this work could help to further improve the understanding of the actual role of inhibitors during high-temperature annealing and could also provide new ideas for further improving the industrial production process.

Influence of Fine Precipitates on Primary Recrystallization Mechanism and Texture Formation in Cold Rolled Fe-3%Si Alloy with Initial Coarse Goss Grains

Influence of Fine Precipitates on Primary Recrystallization Mechanism and Texture Formation in Cold Rolled Fe-3%Si Alloy with Initial Coarse Goss Grains

Influence of solution heating rate on grain structures and fatigue crack propagation behaviors of an aviation Al-Li alloy sheet

In this study, the effects of grain structure on the fatigue crack propagation (FCP) behaviors in the aviation Al-Li alloy sheets prepared by varying solution heating rates are discussed systematically. The results reveal that both the intensity of Goss texture and grain dimensions are improved with the decreased solution heating rates. Upon an identical stress intensity factor range (ΔK), the increased Goss texture of the sample with a solution heating rate of 2 ℃/min (2HR) promotes crack deflection, causing a decrease in FCP rates compared to that of the sample with a solution heating rate of about 100 ℃/min (FHR). The dislocations clustered near grain boundaries are more significant with increasing grain size during cyclic loading, which intensifies the strain localization. The accumulation of dislocations increases the possibility of micro-voids formation and creates the conditions for crack deflection, which results in a decrease in FCP rate. Besides, based on the calculation of the reversible plastic zone (RPZ) size, the initial ΔK entering the rapid propagation region increases with decreasing solution heating rates and exhibits a strong linear relationship with grain size.

Evolution of Microstructure and Texture in Grain-Oriented 6.5% Si Steel Processed by Rolling with Intrinsic Inhibitors and Additional Inhibitors.

A grain-oriented steel containing 6.5% Si, characterized by a notable Goss texture, was effectively manufactured through the rolling technique, incorporating both intrinsic inhibitors and additional inhibitors. This investigation focuses on tracking the development of texture and magnetic properties during the manufacturing process and delineates the mechanism underlying secondary recrystallization. The empirical findings clearly demonstrated the significant influence of nitriding duration and quantity on the secondary recrystallization process. In instances where additional nitrogen is absent, the intrinsic inhibitors alone do not lead to secondary recrystallization. However, when the nitriding duration is 90 s and the nitriding amount is 185 ppm, a complete secondary recrystallization structure with a strong Goss texture enables the finished products have excellent magnetic properties. The preferential growth of Goss grains is mainly governed by the enhanced mobility of high-energy (HE) grain boundaries. With the increase in annealing temperature, the occurrence of 20°-45° HE grain boundaries with Goss grains becomes more progressively frequent. At the secondary recrystallization temperature of 1000 °C, the frequency of 20°-45° HE grain boundaries with Goss grains reaches 62.7%, providing favorable conditions for the abnormal growth of Goss grains. This results in a secondary recrystallization structure predominantly characterized by a strong Goss texture. In light of these observations, the present study provides fundamental theoretical insights and serves as a valuable procedural guideline for the industrial manufacturing of 6.5% Si grain-oriented electrical steels.

Effect of Annealing Time on Texture Evolution of Fe–3.4 wt% Si Nonoriented Electrical Steel

Herein, the effect of annealing time on the texture evolution in Fe–3.4 wt% Si non‐oriented electrical steel is investigated. Strip samples are cast using a vacuum sampling method, which simulate the solidification conditions of an industrial twin roll thin strip casting (TRSC) process. As‐cast samples with different carbon and sulfur (C&amp;S) levels are hot rolled (HR) with varying levels of hot deformation, cold rolled (CR) to 0.35 mm thickness, and then annealed at 1050 °C for different holding times (1, 6, 24 h). To Fe–3.4 wt% Si nonoriented electrical steel, the observed texture evolution can be divided into different stages as annealing time is increased from 1 to 24 h. With increasing annealing time, the fraction of Goss texture decreases initially and then increases again through the consumption of grains with other textures. With additional time, a decrease of pinning force due to precipitate coarsening results in normal grain growth, resulting in an increase of grain size. In this step, Cube grains can form from rotated Goss grains. A model for core loss is presented and used to explain the core loss results.

A quasi-in-situ EBSD study on the formation and development of η-fiber in 0.15 mm ultra-thin Fe-4.5 wt. % Si sheet

Texture evolution of 0.15 mm ultra-thin Fe-4.5 wt. % Si sheet with strong η-fiber produced by two-stage rolling and final annealing was investigated using ex-situ and quasi-in situ electron backscatter diffraction (EBSD). The Goss grain of the hot-rolled plate was rotated to γ-fiber (<111>//ND) dominated by {111}<112> during one stage of moderate warm rolling reduction and then formed strong Goss after intermediate annealing. When the rolling reduction was slightly increased, the annealed strong Goss rotated to near {111}<112> and then formed strong {120}<001> after final annealing. The quasi-in-situ EBSD characterization of the intermediate and final recrystallization process indicated that the recrystallized Goss, {120}<001> and {111}<112> grains were nucleated and grown within the shear bands of deformed {111}<112>, near {111}<112>({223}<362>), and {111}<110> matrices respectively. The recrystallized strong η-fiber textures dominated by {120}<001> were dependent on the coarser Goss grains and suitable rolling reduction and could remain unchanged after considerable grain growth. The 0.15 mm specimen with superior magnetic properties and high strength achieved an iron loss (P10/400 =7.82 W/kg) improvement of 17 %, magnetic induction (B50 =1.65 T) improvement of 0.04 T, and yield strength (474 MPa) improvement of 61 MPa compared to commercial products with the same thickness.

Influence of Fine Precipitates on Primary Recrystallization Mechanism and Texture Formation in Cold Rolled Fe-3%Si Alloy with Initial Coarse Goss Grains

Influence of Fine Precipitates on Primary Recrystallization Mechanism and Texture Formation in Cold Rolled Fe-3%Si Alloy with Initial Coarse Goss Grains

The effects of strain path change on the microstructure, texture, and mechanical properties of accumulative roll-bonded (ARBed) AA1050 strips

In this study, the effect of unidirectional accumulative roll bonding (UARB) and rotational ARB (RARB) on the microstructure, texture, and mechanical properties of AA1050 sheets was investigated. The X-ray diffraction technique was used to study the microstructural and textural evolutions in the processed samples. It was found that the successive sample rotation suppressed the evolution of low-angle grain boundaries (LAGBs) to high-angle ones in the RARBed sheets. However, the grain size was dramatically reduced from 35.7 μm to 169 nm in the starting Al and the processed sample by eight RARB cycles, respectively. Akin to the UARB path, the RARB route led to a drastic drop in Cube {001} <100> texture intensity. Compared to the UARBed strips, additional Goss {011} <100>, A {011} <111>, P {011} <122> and BR {236} <385> components were observed in the RARB-processed sheets. Interestingly, the rotation of Goss-oriented grains towards the Brass {011} <211> component was frustrated by consecutive sample rotation around its normal direction (ND) between RARB passes. In addition to the microhardness test, the uniaxial tensile test was performed at room temperature to evaluate the mechanical properties of the processed aluminum. The results showed that a sharp increase in hardness reached a plateau at higher cycles. In terms of tensile properties, the ultimate tensile strength (UTS) increased to its peak of 332 MPa after eight cycles of the RARB method. Although, their lower interlayer bond strength gave them low elongation compared to their UARBed counterparts.

Dislocation-assisted particle dissolution: A new hypothesis for abnormal growth of Goss grains in grain-oriented electrical steels

The physical mechanisms that lead to the abnormal growth of Goss-oriented grains in grain-oriented electrical steel (GOES) are still not well understood, despite almost a century of research. The present paper reviews the existing hypotheses on the formation of Goss-oriented grains by abnormal grain growth and provides more insights into the underlying mechanism for Goss texture formation by proposing a new hypothesis named “Dislocation-assisted particle dissolution”. Abnormally grown Goss-oriented grains in fully-processed industrial GOES samples are shown to contain a fine network of internal subgrain boundaries with very low angle (0.03° - 0.18°) each consisting of regular arrays of dislocations. These subgrain boundaries form a branched ray-like pattern from the Goss grain center towards its perimeter, i.e. they seem to have evolved with the grain during its growth. Structural and compositional analysis of these dislocations by controlled electron channelling contrast imaging (cECCI) and atom probe tomography (APT) show that these dislocations are enriched with solutes such as Sn, Cu, C, and more importantly, with Al, N and Mn, which all build the composition of the inhibitor particles that assist the abnormal growth of Goss-oriented grains. Additionally, molecular statics (MS) calculations are employed to compare the segregation tendencies of Al atoms on dislocations and on Σ9 boundaries. It is found that Al prefers to segregate to dislocations rather than to the boundaries. The origin and the role of subgrain boundaries are discussed based on the experimental and simulation results. The results indicate that, after the dissolution of inhibitors along the grain boundaries, solutes are absorbed by the subgrain dislocations. As a result, grain boundaries surrounding Goss grains become less decorated by solutes and precipitates and more mobile compared to the boundaries of matrix grains.

Role of inhibitor behavior in abnormal growth of Goss grain in grain-oriented silicon steel: experiments and modeling

The role of inhibitor behavior in abnormal growth of Goss grains during secondary recrystallization was studied in combination with experimental observation and phase-field model simulation in grain-oriented silicon steel. The frequency advantages of both HE (high energy) and CSL (coincidence site lattice) grain boundaries around Goss grains over the matrix were identified, with frequency advantages of ∼15% and ∼2% respectively. The HE grain boundary was supposed to play a more important role in abnormal grain growth over CSL grain boundary in this study. The boundary character distribution was necessary but not sufficient for the abnormal growth of Goss grains. Appropriate inhibitor behavior was a prerequisite for secondary recrystallization. The initial content and stability of inhibitor played a key role in stabilizing the matrix, which guaranteed beneficial fine grains around Goss grains. While if the inhibitor force rapidly declined, matrix grains might grow obviously, resulting in coarsened grain colonies with Cube, {112}<110>, {111}<112>, {411}<148>and {210}<001> orientation, which further hindered the abnormal growth of Goss grains. The candidate Goss grains with different misorientations competed with each other during secondary recrystallization and the exact Goss grain exhibited an obvious growth advantage. Only with an appropriate pinning force and grain boundary character, perfect secondary recrystallization can be achieved. The present findings can provide guidance to understand and precise control of abnormal grain growth phenomenon.

Secondary recrystallization of Goss texture in one-stage cold rolled Fe–Ga thin sheets via a large rolling reduction

Preparing Fe–Ga sheets with excellent magnetostrictive coefficients by rolling and annealing methods can greatly promote the development of high-efficiency magnetostrictive devices. 0.3 mm thick Fe–Ga thin sheet was produced by the one-stage large-reduction cold rolling method without intermediate annealing. Trace V and Nb elements addition improves the rolling formability of the Fe–Ga sheet by precipitating a large number of (Nb,V)C particles. The evolution of precipitation, microstructure, texture, and magnetostrictive coefficients in the Fe–Ga sheet was investigated. The microstructure of primary recrystallization is composed of homogenous distribution of fine grains with an average grain size of about 22 μm. The composite inhibitors composed of MnS and (Nb,V)C precipitates with a particle size of 40∼80 nm suppress the matrix grains effectively. The primary recrystallization texture consists of a strong γ texture with a peak at {111}&amp;lt;112&amp;gt; and a relatively strong {114}&amp;lt;481&amp;gt; texture. The secondary recrystallization of Goss grain occurs at the annealing temperature of 900 °C and is completed at 1100 °C by the combined effects of the existing inhibitor and texture. The Fe–Ga thin sheets composed of several millimeter-sized grains of Goss texture accompanied by small grains oriented by {114}&amp;lt;481&amp;gt; were obtained after annealing at 1100 °C, and its measured magnetostriction value is about 238 ppm. The present work proposes a promising routine to produce high-performance Fe–Ga thin sheets.

Enhanced magnetostriction of rolled (Fe81Ga19)99.93Tb0.07 thin sheet by synergy strategy of secondary recrystallization and trace Tb-doping

Improving the magnetostriction of Fe-Ga thin sheets can significantly promote the magneto-mechanical conversion efficiency of Fe-Ga alloy devices at high-frequency magnetic fields. In this paper, the rolled (Fe81Ga19)99.93Tb0.07 thin sheet with excellent magnetostriction was developed by the synergy strategy of secondary recrystallization and trace Tb-doping. Centimeter-sized Goss grains were induced 0.27 mm-thick (Fe81Ga19)99.93Tb0.07 thin sheet by a composite inhibitor composed of nanometer-sized sulfides and Tb-rich precipitates. The remarkable reduction of the Tb-rich precipitates after quenching led to the dissolution of terbium in the matrix and result in the formation of the Tb-doping induced L60 nanoheterogeneities, which enhancing the lattice distortions in the matrix. The final saturation magnetostriction and the magnetostriction parallel to the rolling direction in (Fe81Ga19)99.93Tb0.07 thin sheets reached 378 ppm and 320 ppm, respectively, which is 30 % and 65 % greater than the undoped thin sheets. This Fe-Ga thin sheet with excellent magnetostriction, produced by a conventional rolling, annealing and quenching method, can greatly improve the conversion efficiency and apply to the next-generation magnetostrictive materials.